The present invention is directed to network communications.
A communications network such as network 100 of FIG. 1a may include a plurality of stations or nodes (Central Node and nodes A-E) coupled by transmission media (e.g., cable wire or optical fiber) providing a path for the transmission of data (e.g., E-mail, video, multimedia, or voice) between two or more nodes. The data may be transferred in accordance with a network protocol (e.g., Internet Protocol (IP), asynchronous transfer mode (ATM), or synchronous optical network/synchronous digital hierarchy (SONET/SDH)) over optical transmission media. The network 100 may include one or more central nodes and one or more branch nodes (A-E) connected by an inner ring 126 and an outer ring 146. The network configuration may be based on a dual ring topology, where data is transmitted from a source node to a destination node (often through intermediary nodes) by transmitting data along one of two rings, where the rings have traffic flowing in opposing directions (clockwise direction 110 or counterclockwise direction 111). Control information may be routed in a direction opposite the control information's respective data. As data enters each successive node, local data is split off and transit data passes through the node along the ring.
In a conventional network using a dual-ring topology, when there is a fault in one of the rings (for example, fault 191 in FIG. 1b) between two nodes (B and C), the data on both inner ring 126 and outer ring 146 is wrapped (i.e., the packets are redirected to the unbroken ring) in the two adjacent nodes (B and C, via paths 171b and 172b) to bypass the fiber paths between the two nodes (one path of which does not have a fault). Typically, the data is also wrapped between the nodes (B and C, via paths 171a and 172a) in a way that some host data entering the ring at a node adjacent to the break is dropped.
Like reference symbols in the various drawings indicate like elements.